There are three (3) main types of foundations for homes and they are concrete slabs, crawl spaces and basements.
Sometimes referred to as slab-on-grade, the concrete slab is the easiest and least expensive foundation to build. A slab-on-grade is a flat concrete pad pored directly onto the ground, taking very little excavation, form work or labor. The day after the slab is poured, wall framing can often begin. It consists of concrete beams that are placed about 2 feet deep into the soil. Then, a 4 to 6 inch layer of gravel is put down, covered by a 4-millimeter sheet of plastic to keep the moisture out, and then a 4 to 6 inch layer of concrete is poured on top of that. Any sewer pipes and possibly electrical conduit must be in place before the concrete is poured. These are embedded in the slab. While this is less expensive than a basement or crawl space, you are limited if you want to add plumbing after the slab has been poured. A slab-on-grade is frequently used in two ways: either as the bottom floor of a home or as a floor of a home with a daylight basement where the floor is about even with the outside earth. These are mostly commonly used in warmer climates with mild winters not requiring a deep foundation.
Crawl space is a step or two above a slab and is defined as the space between the bottom floor and the earth. It is typically anywhere from 18 inches to four feet high and is enclosed with cement or cinder blocks which have been placed on a concrete beam. The concrete or cinder blocks may be covered on the exterior with brick. A crawl space is less expensive to build than a basement and is comparable in price to a slab foundation. The duct work and plumbing can run the crawl space allowing for ease of service and repair. The floor system over and the foundation walls inside of the crawl space almost always need to be insulated.
Basements can be a good choice for sites that slope steeply and in climates having cold winters with frost penetration. It consists of a hole about 8 feet deep at the bottom of which is a concrete slab. The outer walls consist of either concrete or cinder blocks which rest on a concrete beam. If the outer walls are concrete, you may choose to use Insulated Concrete Forms or ICF which are forms or molds that have built-in insulation for accepting reinforced concrete. Ask any homeowner who has a basement, and they will often tell you they would never be without one. The cost per square foot for this bonus space is often a fraction of what you pay for the living space stacked above it. If you do an actual cost analysis of a full height foundation versus a crawl space, you will find it costs very little to upgrade to the full foundation. If you can afford the extra cost, ask your contractor to consider extra height foundation walls that allow you to have a clear ceiling height of eight feet or more beneath any and all beams that support floor joists. Depending on your region, site conditions and design of your dream home, one of these foundation types will be right for you. Your architect or designer can help you decide which of these are best for your project.